Dual rate machine gun with gas chamber encircling the barrel



Oct. 18, 1960 R. BARR EI'AL DUAL RATE MACHINE GUN WITH GAS CHAMBER ENCIRCLING THE BARREL Filed Nov. 2, 1954 FIG. 5

FIG. 4

IRWIN R. BARR PATRICK ESWEENEY INVENTORS y ma g g m TORNE Y United States Patent DUAL RATE MACHINE GUN WITH GAS CHAMBER EN CIRCLING THE BARREL Irwin R. Barr, Kingsville, and Patrick E. Sweeney, Baltimore, Md., assignors to Aircraft Armaments, Inc., Baltimore, Md., a corporation of Maryland Filed Nov. 2, 1954, Ser. No. 466,312

12 Claims. (Cl. 89-129) This invention relates to machine guns and more particularly to a gun adapted to have a dual rate of fire.

It is well known that the most desirable rate of fire for a machine gun is dictated by the use to which the gun is put, so that the most suitable rate for ground to ground defense would not be the most effective rate against high speed aircraft. For this reason it is desirable to provide a gun having a variable rate of fire 'so that it may be utilized effectively in more than one type of tactical situation. For reliable operation, however, it is desirable that such a gun be extremely simple in design and rugged in construction.

The gun herein proposed by the applicants combines all of these features, and provides a method for adapting a conventional machine gun to dual rate operation, which method is suitable for use with most recoil operated guns.

Briefly, the proposed device comprises a gas chamber encircling the barrel of a conventional recoil operated gun, into which chamber a portion of the propelling gas is admitted as the projectile passes through the gun barrel. An annular piston also surrounding the barrel and operating within the gas chamber is acted upon by the gases to provide additional acceleration during the recoil motion of the barrel. A collar carried by the gun barrel functions to shut ed the supply of gas to the chamber at the proper point to give the desired rate of fire. The position of the collar on the gun barrel may be adjusted to close off the gas supply to the chamber during the entire recoil cycle if desired, so that a low rate of fire may be obtained.

It is the object of this invention, therefore, to provide a machine gun having a dual rate of fire.

It is another object of this invention to provide a gas operated recoil booster for a recoil operated machine gun.

It is a further object of this invention to provide a simple and effective means for changing the rate of fire of a machine gun by selectively rendering a recoil booster operative or inoperative.

These and further objects will become apparent from the following description and the accompanying drawings and claims.

In the drawing:

Figure 1 is a partial sectional view of a machine gun incorporating the recoil booster of this invention and showing the booster in the high rate of fire position.

Figure 2 is a sectional view showing an intermediate position of the gun barrel during recoil in the high rate of fire position.

Figure 3 is a sectional view showing the exhaust position of the barrel during high rate of fire operation.

Figure 4 is a sectional view showing the recoil booster in the inoperative position.

Figure 5 is a cross sectional view taken along line 5-5 of Figure 1.

Figure 1 shows a machine gun 1 comprising a recoiling barrel 2 contained within a barrel support 3. The barrel support is fixed to the receiver 4 of the gun and consequently does not move during the gun operation. A portion of the barrel 2 forms a piston 15 having a diameter ice somewhat greater than the remainder of the barrel. The forward portion of the piston 15 is reduced in diameter to form a shoulder or piston face 13 encircling the gun barrel. A recoil booster in the form of cylindrical collar or sleeve 5 encircles the gun barrel at the piston 15, the inner diameter of the collar forming a cylinder 14 in which the piston 15 reciprocates. A peripheral groove is formed around the inner diameter of the collar 5 to form a gas chamber 7 as may be seen in Figures 1 and 5. Sealing rings 11 are provided to allow reciprocating mo tion of the barrel within cylinder 14 while maintaining gas pressure therein. A series of gas passages 8 extend from the bore 9 of the barrel 2 to a point just behind the piston face 13 and serve to admit a portion of the propelling gases to the chamber 7 as will be hereinafter described. A series of exhaust ports 10 extend from cylinder 14 to the atmosphere. Collar 5 is attached to the support 3 by means of threads 6 and is rotatable for axial adjustment along the barrel 2.

For high rate of fire operation, the collar 5 is rotated on threads 6 to its rearmost position as shown in Figures 1, 2 and 3. When the gun is fired, the projectile 12 moves toward the muzzle end of the barrel 2 and uncovers the gas passages 8 when in the position shown in Figure 2, admitting a portion of the propelling gases into the gas chamber 7. Piston face 13 is acted upon by the gas pressure in the chamber 7 to increase the rearward acceleration of the barrel which has already begun to re coil due to the gas pressure acting against the cartridge case at the chamber end of the barrel. As the barrel moves rearwardly, the expanding gases are trapped in the chamber 7 when gas passages 8 are disconnected there'- from by the walls of cylinder 14. This action can readily be seen from inspection of Fig. 2. The trapped gases continue to act against piston face 13, as shown in Figure 2, so that the barrel is accelerated rearwardly after the time at which the projectile leaves the barrel and the gas pressure therein has been dissipated.

When the recoiling barrel reaches the position shown in Figure 3, the gases in the chamber 7 are allowed to expand into the atmosphere through exhaust ports 10, while the barrel continues to move to its rearmost position and return to battery to complete the cycle.

To obtain the low cyclic rate, the booster cylinder 5 is rotated on the threads 6 to its forward position as shown in Figure 4 so that the gas passages 8 are closed during the entire cycle and the rearward acceleration of the barrel is due entirely to the gas pressure within the bore 9 acting on the cartridge case at the chamber end of the barrel.

The rate of fire during high rate operation is governed by the area of the piston 13 and the propelling gas pressure which, in turn, depends on the location of the gas passages 8 along the barrel. Thus the proper combination of piston area and position of the gas passages can be selected to give the desired high rate of fire for a particular application of the gun.

This arrangement provides a very effective and extremely simple and reliable method for adapting a machine gun to a dual rate of fire. It requires the addition of but a single part which does not materially increase the weight of the gun. Because of the basic simplicity of the device, operation of the gun at either of the available rates of fire is exn'emely reliable, and gun stoppages due to malfunctioning of the booster are practically non-existent.

Although not shown in the drawing, it is obvious that by providing more than one set of gas passages and suitably modifying the booster cylinder 5, as many difierent rates of fire as desired may be obtained.

While but one embodiment of the present invention has been shown and described, it is apparent that many modifications and changes can be made without departing from the spirit of the invention or the scope of the appended claims.

We claim:

1. A machine gun comprising a fixed housing, a barrel having a bore and being reciprocable with respect to said housing, means carried by said housing and forming a chamber encompassing a portion of said barrel, means forming a piston carried by said barrel for reciprocating motion within said chamber, a port means communicating with the bore of said barrel and said chamber during a first portion of the travel of said barrel, means for closing said port during a second portion of said travel and a second port means communicating with said chamber and the exterior of said gun during a third portion of the travel of said barrel.

2. A machine gun comprising a housing, a barrel cyclically reciprocable with respect to said housing, a collar adjustably carried by said housing and encircling a portion of said barrel and having means to form a chamber therebetween, a shoulder carried by said barrel forming a piston reciprocable within said chamber, first port means communicating with said chamber during a portion of the travel of said barrel for admitting a portion of the projectile propelling gases into said chamber during the firing of said gun, said gases adapted to act upon said piston to accelerate said barrel, second port means communicating with said chamber during a second portion of the travel of said barrel for allowing said gases to escape from said chamber, said collar having closing means adapted to be positioned to close said first port means durmg the entire travel of said barrel to prevent said gases from entering said chamber and accelerating said barrel. 3. A machine gun comprising a supporting structure, a gun barrel having a bore and being reciprocable between forward and rear positions with respect to said structure, said gun barrel having a major and a minor outside diameter forming a shoulder therebetween, means carried by said supporting structure and forming a cylinder surrounding a portion of the length of said barrel including said shoulder, said cylinder having major and minor inner diameters closely encompassing said major and minor outer diameters of said barrel respectively, an annular groove forming a chamber within said cylinder between said major and minor inner diameters, a passage connecting the bore of said barrel with said chamber during a first portion of the rearward motion of said barrel, a passage extending through the wall of said cylinder and connecting with said chamber during a second portion of the rearward travel of said barrel, means on said cylinder to close said passage when said barrel is intermediate said positions, and means for moving said cylinder axially along said barrel to position said chamber forward of the foremost position of the first said passage.

4. A machine gun comprising a support, a gun barrel having a bore and being arranged for axial movement between forward and rear positions with respect to said support, means carried by said support forming a cylin d er encompassing a portion of said barrel, a piston carrled by said barrel for reciprocating motion within said cylinder, passage means interconnecting the bore of said barrel and said cylinder at one position of said barrel, means on said cylinder to disconnect said interconnecting passage means at another position of said barrel, passage means connecting said cylinder with the atmosphere at a different position of said barrel, and means for positionmg said cylinder means to prevent the first said passage means from interconnecting the bore of said barrel and said cylinder at any position of said barrel.

5. In a machine gun, having a stationary support and a gun barrel reciprocally mounted therein with said barrel adapted to be moved from a projected position to a retracted position when a projectile is fired therethrough};

the improvement comprising means adapted to be acted upon by expandable gases generated when said projectile is fired to accelerate said barrel toward retracted P i 4 and means on said support selectively adjustable between an operative condition for etfecting operation of said first named means and an inoperative condition for preventing operation of said first named means.

6. The combination, with a machine gun of the type having a support and gun barrel movable relative to said support from an in-battery position to a recoiled position when a projectile is fired therethrough, of means on said barrel adapted to be acted upon by expandable gases generated by firing said. projectile whereby the recoil of said barrel is accelerated, passage means on said barrel effective to pass said gases thereth'roug'h upon initial recoil of the barrel so that said gases can act on said first named means, and control means on said support selectively operable from a position whereby said passage means is efiective to a position whereby said passage means is blocked.

7. In a machine gun having a stationary support, the combination of a recoilable gun barrel mounted in said support for movement between a projected position and a retracted position, port means in said barrel, piston means associated with said barrel for movement therewith, sleeve meansattached to said support and forming with said piston means an enclosed chamber connecting with said port means only when said barrel is in substantially projected position, means to disconnect said port means from said chamber as said barrel moves toward said retracted position, and means selectively operable to disconnect said port means from said chamber when said barrel is in said substantially projected position.

8. A machine gun of the type having a gun barrel reciprocably mounted in a stationary support, a piston attached to and movable with said barrel in a cylinder which is attached to said support, and port means in said barrel for conducting expandable gases into said cylinder upon recoil of the same, characterized by the provision of means on said support selectively adjustable between a first position for efiecting the conduction of said expandable gases and a second position for preventing such conduction.

9. In a weapon of the class described having a support and a gun barrel reciprocally mounted therein for movement between in-battery and recoiled positions when a projectile is fired therein, means to adjust the time required for such movement comprising: port means in said barrel adapted to pass expandable gases therethrough upon movement of said barrel toward recoiled position, a piston attached to said barrel for movement therewith, cylinder means on said support associated with said piston and adapted to receive said expandable gases from said port means whereby said gases can expand against said piston to accelerate movement of said barrel toward retracted position, vent means elfective to vent said cylinder only when said barrel is substantially in recoiled position, and means on said support movable and adjustable relatively thereto between a first position for effecting the function of said port means and a second position for preventing such function, whereby in the first position said last named means shortens the time required for movement of said barrel aforesaid as compared to the time required when said-last named means is in the second position.

10. In a machine gun having a stationary support and a recoilable barrel mounted therein for cyclical movement between in-battery and recoiled positions upon the cyclical firing of projectiles, means to vary the rate of such cyclical movement, said means comprising in combination: a piston having a face mounted on said barrel for movement therewith, a sleeve mounted on said support having means defining with said face an enclosed chamber within which expandable gases generated by said firing are adapted to be contained so as to act upon said face and thereby move the piston and barrel together, port means in said barrel for conducting expandable gases from the bore of said barrel into said chamber each time a projectile passes said port means as said barrel is moving toward recoiled position, vent means for venting the gases contained in said chamber, means on said sleeve for preventing such venting until said barrel is substantially at said retracted position, and means mounted on said support selectively adjustable relative thereto between a position for effecting conduction of said gases through said port means and a position for preventing such conduction whereby the rate of said cyclical movement when said last named means is in the former position is greater than when the same is in the latter position.

11. In combination, a support adapted to be attached to a machine gun mounting, a recoilable gun barrel reciprocably mounted therein, a shoulder onsaid barrel forming a piston face upon which expandable gas is adapted to act, a sleeve mounted on said support having means thereon encircling said shoulder to form thereby a cylinder within which said piston face is movable, port means in said barrel for conducting expandable gases therethrough, conducting means effective during initial recoil for conducting said gases into said cylinder, means becoming effective thereafter upon funther recoil to trap said gases therein whereby the same are adapted to expand against said piston face and thereby accelerate said recoil, and means mounted on said support selectively movable from one position for effecting operation of said conducting means to achieve the result aforesaid to another position for preventing operation of said conducting means to prevent the result aforesaid.

12. The device of claim 11, wherein said sleeve is provided with vent means for venting said gases after expansion in said cylinder, and means for preventing operation of said vent means until recoil of the barrel is completed.

References Cited in the file of this patent UNITED STATES PATENTS 726,399 Burgess Apr. 28, 1903 929,491 Reifgraber July 27, 1909 1,381,016 Reising June 7, 1921 2,252,754 Browning Apr. 18, 1941 2,409,225 Schaich Oct. 15, 1946 2,756,639 Bird July 31, 1956 FOREIGN PATENTS 922,333 France Feb. 13, 1946 

